Reducing pigments

ABSTRACT

The present invention relates to platelet-shaped pigments that comprise a layer obtained by calcining TiO 2 /SiO y  or TiO 2 /metal, especially TiO 2 /AI (0.03≦y≦1.95, especially 0.03≦y≦1.8, more especially 0.70≦y≦1.8), and to the use thereof in paints, textiles, ink-jet printing, cosmetics, coatings, plastics, printing inks, in glazes for ceramics and glass, and in security printing. The pigments according to the invention are distinguished by a high gloss and a very uniform thickness, as a result of which very high color purity and color strength are obtained.

The present invention relates to platelet-shaped pigments that comprisea layer obtained by calcining TiO₂/SiO_(y) or TiO₂/metal, especially Ti,Zr, Cr, or Zn, more especially Al (0.03≦y≦1.95), and to the use thereofin paints, textiles, ink-jet printing, cosmetics, coatings, plastics,printing inks, in glazes for ceramics and glass, and in securityprinting.

The pigments according to the invention are distinguished by a highgloss and a very uniform thickness, as a result of which very highcolour purity and colour strength are obtained.

The known titanium dioxide reducing pigments are based on the use ofmica or titanium dioxide platelets as the base substrate. The titaniumdioxide is applied to the coated or non-coated base substrates byprecipitation and is subsequently reduced to titanium suboxides. Gaseousreducing agents, such as hydrogen or ammonia, or metals, such as, forexample, silicon or titanium, are generally used as the reducing agents.

U.S. Pat. No. 4,948,631 discloses a process for the preparation ofparticularly bluish pearl lustre pigments by reduction of mica pigmentscoated with titanium dioxide with ammonia at temperatures of from 750 to850° C.

JP H4-20031 describes a process for the preparation of a coloured micapigment by mixing a mica pigment coated with titanium dioxide withtitanium and reducing the resuming mixture in vacuo at from 500 to 1000°C.

DE-A-19618562 discloses a titanium dioxide reducing pigment consistingof titanium dioxide, titanium suboxides and, where appropriate, afurther metal dioxide or titanium oxynitrite. That pigment is obtainedby solidifying an aqueous solution of a thermally hydrolysable titaniumcompound on an endless belt, detaching the resulting layer, coating theresulting titanium dioxide platelets with further titanium dioxide bythe wet process, drying and, where appropriate, calcining and treatingin a non-oxidising gas atmosphere.

A disadvantage of the known pigments, however, is that they have a toolow hiding power and/or do not exhibit colour flop.

A high-gloss, platelet-shaped titanium reducing pigment based on SiO₂platelets is described in DE-A-19843014. The titanium reducing pigmentis obtained by mixing SiO₂ platelets coated with TiO₂ and, whereapplicable, with at least one further metal oxide, with at least onesolid reducing agent in a ratio of from 100:1 to 5:1, and calcining themixtures in a non-oxidising gas atmosphere at a temperature of more than600° C.

Surprisingly, it has now been found that pigments based on SiO_(y) ormetal platelets, especially Ti, Zr, Cr, or Zn platelets, more especiallyAl platelets with high gloss and colour flop, can also be obtained whenTiO₂-coated SiO_(y) platelets, wherein 0.03≦y≦1.95, or TiO₂-coated metalplatelets, in particular Al platelets, are first calcined in anon-oxidising gas atmosphere at a temperature of more than 600° C., andparticularly the TiO₂-coated SiO_(y) platelets are then treated, whereappropriate, at a temperature of more than 200° C., preferably more than400° C. and especially from 500 to 1000° C., with air or anotheroxygen-containing gas.

BRIEF DESCRIPTION OF THE DRAWIFIG

FIG. 1 shows the reflection spectra at 10 degrees 65 degrees of Samples1 and 2.

The present invention accordingly relates to a platelet-shaped pigmentcomprising a layer obtained by calining TiO₂/SiO_(y) wherein0.03≦y≦1.95, especially 0.03≦y≦1.80, more especially 0.70≦y≦1.80, orTiO₂/metal, in particular TiO₂/Al.

The particles of the platelike pigments generally have a length of from1 μm to 5 mm, a width of from 1 μm to 2 mm, and a thickness of from 20nm to 2 μm, and a ratio of length to thickness of at least 2:1, theparticles having two substantially parallel faces, the distance betweenwhich is the shortest axis of the core.

The flakes of the present invention are not of a uniform shape.Nevertheless, for purposes of brevity, the flakes will be referred to ashaving a “diameter.” The flakes have a high plane-parallelism and adefined thickness in the range of ±30%, especially ±10%, most preferred+/−5% of the average thickness. They have a thickness of from 20 to 2000nm, especially from 100 to 350 nm. It is presently preferred that thediameter of the flakes be in a preferred range of about 1-60 μm with amore preferred range of about 5-40 μm.

The term “SiO_(y) with 0.03≦y≦1.95” means that the molar ratio of oxygento silicon at the average value of the silicon oxide layer is from 0.03to 1.95. The composition of the silicon oxide layer can be determined byESCA (electron spectroscopy for chemical analysis). SiO_(x), SiO_(x1),SiO_(x2), SiO_(y1), and SiO_(z) are defined accordingly.

According to the present invention the term “aluminum” comprisesaluminum and alloys of aluminum. Alloys of aluminum are, for exampledescribed in G. Wassermann in Ullmanns Enzyklopädie der IndustriellenChemie, 4. Auflage, Verlag Chemie, Weinheim, Band 7, S. 281 to 292.Especially suitable are the corrosion stable aluminum alloys describedon page 10 to 12 of WO00/12634, which comprise besides of aluminumsilicon, magnesium, manganese, copper, zinc, nickel, vanadium, lead,antimony, tin, cadmium, bismuth, titanium, chromium and/or iron inamounts of less than 20% by weight, preferably less than 10% by weight.

Preference is given to pigments comprising

-   (a) a substrate layer of SiO_(z), wherein 0.03≦z≦2.0,-   (b) an intermediate layer obtained by calcining TiO₂/SiO_(y),    wherein 0.03≦y≦1.8, in a non-oxidising atmosphere and-   (c) a TiO₂ layer, or    to pigments comprising-   (a) a substrate layer of Al,-   (b) an intermediate layer obtained by calcining TiO₂/Al in a    non-oxidising atmosphere and-   (c) a TiO₂ layer,    special preference being given to pigments based on SiO_(z)    platelets or Al platelets the entire surface of which is coated with    TiO₂ and which are then calcined in a non-oxidising atmosphere.

Depending on the layer thicknesses of the TiO₂ and the SiO_(y) layer andon the process parameters selected in the calcining process, the entireTiO₂ or SiO_(y) layer may become incorporated in the intermediate layer,producing in that case platelet-shaped pigments having only a substratelayer (a) and an intermediate layer (b) or an intermediate layer (b) anda TiO₂ layer (c).

In that embodiment, the invention accordingly relates to platelet-shapedpigments the particles of which generally have a length of from 2 μm to5 mm, a width of from 2 μm to 2 mm and a thickness of from 20 nm to 1.5μm, and a length to thickness ratio of at least 2:1, the particleshaving a core of SiO_(z) or Al with two substantially parallel faces,the distance between which faces is the shortest axis of the core, andhaving a TiO₂ layer applied to the parallel faces, and preferably to theentire surface, of the core, there being arranged between the SiO_(z) orAl substrate and the TiO₂ layer an intermediate layer obtained bycalcining TiO₂/SiO_(y), wherein 0.03≦y≦1.8. The pigments may, whereappropriate, have further layers on top of the TiO₂ layer.

The thickness of the SiO_(z) layer is generally from 20 to 1000 nm,preferably from 50 to 500 nm, and that of the TiO₂ layer is generallyfrom 1 to 200 nm, especially 10 to 100 nm, more especially from 20 to 50nm.

The invention also relates to the use of the pigments according to theinvention in paints, textiles (EP02405889.3), ink-jet printing(EP02405888.5), cosmetics (WO/03076520), printing inks, plastics,coatings (WO03/068868), especially in automotive finishes, in glazes forceramics and glass, and in security printing.

The pigments based on SiO_(z) or Al platelets are obtained by calciningTiO₂-coated SiO_(y) or Al platelets, wherein 0.03≦y≦1.95, especially0.03≦y≦1.80, more especially 0.70≦y≦1.80, in a non-oxidising gasatmosphere at a temperature of more than 600° C. (below 600° C. withAl), preferably in the range from 700 to 1100° C., for more than 10minutes, preferably for from 15 to 120 minutes. Particularly thepigments based on the SiO_(y) platelets can then be treated, at atemperature of more than 200° C., preferably more than 400° C. andespecially from 500 to 1000° C., with air or another oxygen-containinggas.

The TiO₂-coated SiO_(y) or metal platelets, in particular Al platelets,can basically be obtained by means of a process comprising the followingsteps (WO03/068868):

-   a) vapour-deposition of a TiO₂ layer onto a carrier,-   b) vapour-deposition of an SiO_(y) layer or a metal layer, in    particular an aluminium layer, onto the TiO₂ layer obtained in step    a), and-   c) vapour-deposition of a TiO₂ layer onto the SiO_(y) layer or metal    layer obtained in step b).    Preferably, a separating agent is vapour-deposited onto the carrier    before step a), to produce a separating agent layer which    facilitates separation of the flakes from the carrier.

Preferably, however, first SiO_(y) or Al flakes are produced which arethen coated with TiO₂ by wet-chemical application.

The invention is illustrated below in more detail with reference to Alas metal layer without limiting the scope thereof.

There may be used as Al substrate Al platelets punched from Al foil orAl pigments produced by known atomising and grinding techniques.Preferably, Al flakes produced by means of physical vapour depositionare used (see, for example, U.S. Pat. No. 4,321,087, WO00/24946). Such aprocess comprises the following steps:

-   a) vapour-deposition of a separating agent onto a carrier to produce    a separating agent layer,-   b) vapour-deposition of an Al layer onto the separating agent layer,-   c) dissolution of the separating agent layer in a solvent and-   d) separation of the Al flakes from the solvent

The aluminium pigments may then be coated with titanium dioxide by thechemical vapour deposition (CVD) process, for example in accordance withEP-A-38428. In that process, TiCl₄ vapour is allowed to react in lowconcentration with H₂O vapour in a fluidised bed in the presence ofwarmed moving Al particles.TiCl₄+2 H₂O+Al pigment→TiO₂/Al pigment+4 HCl

The titanium-dioxide-coated Al flakes are then calcined in anon-oxidising gas atmosphere at a temperature below 600° C., for morethan 10 minutes, preferably for from 15 to 120 minutes. The reductionreaction takes place in a non-oxidising gas atmosphere, such as, forexample, N₂, Ar, He, CO₂, H₂ or NH₃, preference being given to N₂ or Ar.In the case of N₂ or NH₃, TiN or TiON may be produced in addition toTiO_(2-x).2 Al+6 TiO₂→Al₂O₃×3 Ti₂O₃2 Al+3 TiO₂→Al₂O₃×3 TiO

The titanium-dioxide-coated reducing pigments may then be coated withfurther inorganic coatings, such as, for example, a Fe₂O₃, chromiumoxide, or CrOOH, SiO₂, Al₂O₃ or ZrO₂ coating.

It is especially advantageous to use SiO_(y) flakes as startingmaterial. Platelet-shaped SiO_(y) substrates wherein 0.95≦y≦1.95,preferably wherein 1.0≦y≦1.80, can be obtained by means of a processcomprising the following steps (see WO03/068868):

-   a) vapour-deposition of a separating agent onto a carrier to produce    a separating agent layer,-   b) vapour-deposition of an SiO_(y) layer onto the separating agent    layer,-   c) dissolution of the separating agent layer in a solvent and-   d) separation of the SiO_(y) flakes from the solvent.

The process mentioned above makes available SiO_(z) substrates that,compared with natural mica platelets and with platelets produced in wetprocedures, have a high degree of plane parallelism and a definedthickness in the region of ±30%, preferably ±10%, most preferred +/−5%,of the average thickness.

SiO_(y) substrates or layers, wherein 0.70≦y≦0.99, are formed preferablyby evaporating silicon monoxide containing silicon in an amount up to20% by weight at temperatures of more than 1300° C. If, under industrialvacuums of a few 10⁻² Pa, Si is vaporised (instead of Si/SiO₂ or SiO/Si)silicon oxides can be obtained which have an oxygen content of less than0.95, that is to say SiO_(x), wherein 0.03≦x≦0.95, especially0.05≦x≦0.50, very especially 0.10≦x≦0.30 (WO03/076520).

The SiO_(y) layer wherein 0.95≦y≦1.95, preferably 1.0≦y≦1.80, in step b)is preferably vapour-deposited from a vaporiser containing a chargecomprising a mixture of Si and SiO₂, SiO_(y), or a mixture thereof. TheSiO_(y) layer is obtained by heating a preferably stoichiometric mixtureof fine silicon and quartz (SiO₂) powder in a vaporiser described, forexample, in DE-C-4342574 and in U.S. Pat. No. 6,202,591 to more than1300° C. under a high vacuum. The reaction product is silicon monoxidegas, which under vacuum is directed directly onto the passing carrier,where it condenses as SiO. Non-stoichiometric mixtures may also be used.The vaporiser contains a charge comprising a mixture of Si and SiO₂,SiO_(y), or a mixture thereof, the particle size of the substances thatreact with one another (Si and SiO₂) being advantageously less than 0.3mm. The weight ratio of Si to SiO₂ is advantageously in the range from0.15:1 to 0.75:1 (parts by weight); preferably, a stoichiometric mixtureis present SiO_(y) present in the vaporiser vaporises directly. Si andSiO₂ react at a temperature of more than 1300° C. to form siliconmonoxide vapour. The separating agent condensed onto the carrier may bea lacquer, a polymer, such as, for example, those described in U.S. Pat.No. 6,398,999 (thermoplastic polymers), especially acrylic or styrenepolymers or mixtures thereof, an organic substance soluble in organicsolvents or water and vaporisable in vacuo, such as anthracene,anthraquinone, acetamidophenol, acetylsalicylic acid, camphoricanhydride, benzimidazole, benzene-1,2,4-tricarboxylic acid,biphenyl-2,2-dicarboxylic acid, bis(4-hydroxyphenyl)sulfone,dihydroxyanthraquinone, hydantoin, 3-hydroxybenzoic acid,8-hydroxyquinoline-5-sulfonic acid monohydrate, 4-hydroxycoumarin,7-hydroxycoumarin, 3-hydroxynaphthalene-2-carboxylic acid, isophthalicacid, 4,4-methylene-bis-3-hydroxynaph-thalene-2-carboxylic acid,naphthalene-1,8-dicarboxylic anhydride, phthalimide and its potassiumsalt, phenolphthalein, phenothiazine, saccharin and its salts,tetraphenylmethane, triphenylene, triphenylmethanol or a mixture of atleast two of those substances. The separating agent is preferably aninorganic salt soluble in water and vaporisable in vacuo (see, forexample, DE-A-19844357), such as sodium chloride, potassium chloride,lithium chloride, sodium fluoride, potassium fluoride, lithium fluoride,calcium fluoride, sodium aluminium fluoride and disodium tetraborate.

Step c) is usually carried out at a pressure that is higher than thepressure in steps a) and b) and lower than atmospheric pressure.

The movable carrier preferably comprises one or more continuous metalbelts, with or without a polymer coating, or one or more polyimide orpolyethylene terephthalate belts. The movable carrier may furthermorecomprise one or more discs, cylinders or other rotationally symmetricalbodies, which rotate about an axis.

It is possible for a plurality of separating agent layers and siliconsuboxide layers to be vapour-deposited onto the movable carrier in vacuoalternately in succession before their removal by dissolution of thecondensed separating agent layers. The plane-parallel structuresconsisting of SiO_(y) are separated from the solvent of the separatingagent preferably by washing-out and subsequent filtration,sedimentation, centrifugation, decanting or evaporation. Furthermore,the plane-parallel structures (platelets, or flakes) consisting ofsilicon suboxide (SiO_(y)) may, after washing-out of the dissolvedseparating agent contained in the solvent, be frozen together with thesolvent and subsequently subjected to a process of freeze-drying, duringwhich the solvent is separated off as a result of sublimation below thetriple point and the dry silicon suboxide remains behind in the form ofindividual plane-parallel structures.

The silicon suboxide condensed on the movable carrier corresponds to theformula SiO_(y,) wherein 0.95≦y≦1.8, preferably wherein 1.0≦y≦1.8, yvalues of less than 1 being obtained by means of an excess of silicon inthe vaporiser material. Except under an ultra-high vacuum, in industrialvacuums of a few 10⁻² Pa vaporised SiO always condenses as SiO_(y)wherein 1≦y≦1.8, especially wherein 1.1≦y≦1.5, because high-vacuumapparatuses always contain, as a result of gas emission from surfaces,traces of water vapour which react with the readily reactive SiO atvaporisation temperature.

In detail, a salt, for example NaCl, followed by a layer of siliconsuboxide (SiO_(y)) are successively vapour-deposited onto a carrier,which may be a continuous metal belt, passing by way of the vaporisersunder a vacuum of <0.5 Pa. The vapour-deposited thicknesses of salt areapproximately from 20 to 100 nm, preferably from 30 to 60 nm, and thoseof SiO are, depending on the intended use of the product, from 20 to1000 nm, preferably from 50 to 500 nm. On its further course, thebelt-form carrier, which is closed to form a loop, runs through dynamicvacuum lock chambers of known construction (cf. U.S. Pat. No. 6,270,840)into a region of from 1 to 5×10⁴ Pa pressure, preferably from 600 to 10⁹Pa pressure, and especially from 10³ to 5×10³ Pa pressure, where it isimmersed in a separating bath. The temperature of the solvent should beso selected that its vapour pressure is in the indicated pressure range.With mechanical assistance, the separating agent layer rapidly dissolvesand the product layer breaks up into flakes, which are then in the formof a suspension in the solvent. On its further course, the belt is driedand freed from any contaminants still adhering to it. It runs through asecond group of dynamic vacuum lock chambers back into the vaporisationchamber, where the process of coating with separating agent and productlayer of SiO_(y) is repeated.

The suspension then obtained in both cases, comprising productstructures and solvent with separating agent dissolved therein, is thenseparated in a further operation in accordance with a known technique.For that purpose, the product structures are first concentrated in theliquid and rinsed several times with fresh solvent in order to wash outthe dissolved separating agent. The product, in the form of a solid thatis still wet, is then separated off by means of filtration,sedimentation, centrifugation, decanting or evaporation, and is dried.

It is possible to arrange a plurality of separating agent and productvaporisers one after another in the running direction of the belt in thevaporisation zone. By that means there is obtained, with littleadditional outlay in terms of apparatus, a layer sequence of S+P+S+P,wherein S is the separating agent layer and P is the product layer.

Separating off the plane-parallel structures after washing-out atatmospheric pressure can be carried out under gentle conditions byfreezing the suspension, which has been concentrated to a solids contentof approximately 50%, and subjecting it in known manner to freeze-dryingat approximately −10° C. and 50 Pa pressure. The dry substance remainsbehind as product, which can be subjected to the steps of furtherprocessing by means of coating or chemical conversion.

Instead of using a continuous belt, it is possible to produce theproduct by carrying out the steps of vapour-deposition of separatingagent and SiO, of separation, and of drying the carrier, in an apparatushaving a rotary body, in accordance with WO01/25500. The rotary body maybe one or more discs, a cylinder or any other rotationally symmetricalbody.

The substrate may also be a multi-layered substrate, such as, forexample, a multi-layered platelet-shaped substrate layer having a coreof SiO_(x1) that has a SiO_(x2) layer, or a SiO_(y1) layer on the lowerand upper surfaces, but not on the side faces,

a multi-layered platelet-shaped substrate layer having a core ofSiO_(x2) that has a SiO_(x1) layer, or SiO_(y1) layer on the lower andupper surfaces, but not on the side faces,

a multi-layered platelet-shaped substrate layer having a core ofSiO_(y1) that has a SiO_(x1) layer, or SiO_(x2) layer on the lower andupper surfaces, but not on the side faces, or

a multi-layered platelet-shaped substrate layer having a core of ametal, especially Al that has a SiO_(x1) layer, a SiO_(x2) layer, or aSiO_(y1) layer on the lower and upper surfaces, but not on the sidefaces, wherein 0.03≦x1≦0.70, especially 0.05≦x1≦0.50, very especially0.10≦x1≦0.30, 0.70≦x2≦0.99, and 1.00≦y1≦1.95, especially 1.0≦y1≦1.8,very especially 1.1≦y1≦1.8 (PCT/EP03/50229).

The substrate may furthermore be a substrate having a layer structure ofSiO_(y)/metallically reflecting material, preferably a metal having amelting point greater than 1000° C., such as, for example,titanium/SiO_(y), which is obtained by vapour-depositing SiO_(y),metallically reflecting material and SiO_(y) onto the separating agentin succession.

The pigments formed from the multi-layered substrates accordinglycomprise

-   (a) a multi-layered platelet-shaped substrate layer,-   (b) an intermediate layer obtained by calcining TiO₂/SiO_(x1),    TiO₂/SiO_(x2) or TiO₂/SiO_(y1) in a non-oxidising atmosphere and-   (c) a TiO₂ layer,    wherein 0.03≦x1≦0.70, especially 0.05≦x1≦0.50, very especially    0.10≦x1≦0.30, 0.70≦x2≦0.99, and 1.00≦y1≦1.95, especially 1.0≦y1≦1.8,    very especially 1.1≦y1≦1.8.

Coating of the SiO_(y) platelets can be carried out by wet-chemicalapplication, as described, for example, in WO 93/08237, by means ofsol-gel processes or by means of CVD processes, as described, forexample, in DE-A-19614637. Coating of the SiO_(y) platelets ispreferably carried out by wet-chemical application, it being possible touse the procedures developed for pearlescent pigments, which aredescribed, for example, in DE-A-1467468, DE-A-1959988, DE-A-2009566,DE-A-2214545, DE-A-2215191, DE-A-2244298, DE-A-2313331, DE-A-2522572,DE-A-3137808, DE-A-3137809, DE-A-3151343, DE-A-3151354, DE-A-3151355,DE-A-3211602 and DE-A-3235017, DE-A-1959988, WO93/08237, WO98/53001 andWO03/6558.

For coating, the SiO_(y) particles are suspended in water and one ormore hydrolysable titanium salts are added thereto at a pH valuesuitable for hydrolysis which is so selected that the titanium oxides ortitanium oxide hydrates are precipitated directly onto the particleswithout secondary precipitations occurring. The pH value is usually keptconstant by simultaneously metering in a base. The pigments are thenseparated off, washed and dried and, where appropriate, calcined. Ifdesired, the pigments may be separated off, dried and, whereappropriate, calcined after individual coatings have been applied, inorder then to be resuspended for the precipitation of further layers.

The titanium oxide layers are obtainable, for example, analogously to amethod described in DE-A-19501307, by producing the titanium oxide layerby controlled hydrolysis of one or more metallic acid esters, whereappropriate in the presence of an organic solvent and a basic catalyst,by means of a sol-gel process. Suitable basic catalysts are, forexample, amines, such as triethylamine, ethylenediamine, tributylamine,dimethylethanolamine and methoxypropylamine. The organic solvent is awater-miscible organic solvent, such as a C₁₋₄alcohol, especiallyisopropanol.

Suitable titanic acid esters are selected from the group comprisingalkyl and aryl alcoholates, carboxylates, and carboxyl-radical- oralkyl-radical- or aryl-radical-substituted alkyl alcoholates orcarboxylates of titanium. Tetraisopropyl titanate is preferred. Inaddition, acetylacetonates and acetoacetylacetonates of titanium may beused. A preferred example of that type of metallic acid ester istitanium acetylacetonate.

According to a preferred embodiment of the present invention, theprocess described in U.S. Pat. No. 3,553,001 is used for application ofthe titanium dioxide layers. An aqueous titanium salt solution is slowlyadded to a suspension of the material being coated, which suspension hasbeen heated to approximately 50-100° C., especially 70-80° C., and asubstantially constant pH value of approximately from 0.5 to 5,especially approximately from 1.2 to 2.5, is maintained bysimultaneously metering in a base, such as, for example, aqueous ammoniasolution or aqueous alkali metal hydroxide solution. As soon as thedesired layer thickness of precipitated TiO₂ has been achieved, theaddition of titanium salt solution and base is stopped.

That process, also referred to as a titration process, is distinguishedby the fact that an excess of titanium salt is avoided. That is achievedby feeding in for hydrolysis, per unit of time, only that amount whichis necessary for even coating with the hydrated TiO₂ and which can betaken up per unit of time by the available surface of the particlesbeing coated.

The particles based on SiO_(y) platelets wherein 0.03≦y≦1.95, especially0.03≦x1≦0.70, 0.70≦x2≦0.99 and 1.0≦y1≦1.95, especially 1.10≦y1≦1.80, andcomprising (a) a substrate layer of SiO_(y) and (b) a TiO₂ layer, whichare obtained after customary working-up, are novel and the presentinvention relates to them also. If the TiO₂ layer is deposited by a wetchemical process onto the SiO_(y) platelets, the TiO₂ is present on thewhole surface of the SiO_(y) platelets, including the lower and uppersurfaces as well as the side faces of the SiO_(y) platelets.

The TiO₂-coated SiO_(y) platelets are subsequently calcined in anon-oxidising gas atmosphere at a temperature of more than 600° C.,preferably in the range from 700 to 1100° C., for more than 10 minutes,preferably for from 15 to 120 minutes. The reduction reaction takesplace in a non-oxidising gas atmosphere, such as, for example, N₂, Arand/or He, or under a vacuum of less than 13 Pa (10⁻¹ torr), preferencebeing given to N₂ or Ar. In the case of N₂ or NH₃, TiN or TiON may beproduced in addition to TiO_(2-x).

The TiO₂-coated SiO_(y) platelets can optionally be subjected tooxidative heat treatment. For example, air or some otheroxygen-containing gas is passed through the platelets, which are in theform of loose material or in a fluidised bed, at a temperature of morethan 200° C., preferably more than 400° C. and especially from 500 to1000° C. The product can then be brought to the desired particle size bygrinding, treatment with ultrasound, air-classification or sieving, anddelivered for further use.

The pigments based on SiO_(y) platelets and comprising (a) a substratelayer of SiO_(z), wherein 0.03≦z≦2.0, especially 0.10≦y≦2.0, moreespecially 0.70≦y≦2.0, (b) an intermediate layer obtained by calciningTiO₂/SiO_(y), wherein 0.03≦y≦1.95, especially 0.03≦y≦1.80, moreespecially 0.70≦y≦1.80, and (c) a TiO₂ layer, which are obtained in thatcase, are also novel and the present invention relates to them also.

In principle, the anatase form of TiO₂ forms on the surface of thestarting pigment. By adding small amounts of SnO₂, however, it ispossible to force the ruffle structure to be formed by calcination atfrom 800 to 900° C. (see, for example, WO 93/08237 and U.S. Pat. No.4,086,100).

In a further preferred embodiment, the substrate comprises in thisorder:

-   (a1) a SiO_(x1) layer, or a SiO_(x2) layer, especially a SiO_(y1)    layer,-   (b1) a reflective layer, especially a metal layer, and-   (c1) a SiO_(x1) layer, or a SiO_(x2) layer, especially a SiO_(y1)    layer, wherein 0.03≦x1≦0.70, especially 0.05≦x1≦0.50, very    especially 0.10≦x1≦0.30, 0.70≦x2≦0.99, and 1.00≦y1≦1.95, especially    1.0≦y1≦1.8, very especially 1.1≦y1≦1.8.

The substrates comprising layers (a1), (b1) and (c1) are prepared by aprocess comprising the steps:

-   a) vapour-deposition of a separating agent onto a movable carrier to    produce a separating agent layer,-   b1) vapour-deposition of a SiO_(x1) layer, a SiO_(x2) layer, or a    SiO_(y1) layer onto the separating agent layer,-   b2) vapour-deposition of a reflective material, especially titanium    or aluminium, onto the layer obtained in step (b1),-   b3) vapour-deposition of a SiO_(x1) layer, a SiO_(x2) layer, or a    SiO_(y1) layer onto the metal layer,-   c) dissolution of the separating agent layer in a solvent, and-   d) separation of the silicon oxide/reflective material/silicon oxide    particles from the solvent

If step (b3) is omitted, unsymmetrical pigments comprising layers (a1)and (b1) are obtained. The reflective layer consists preferably of ametallic reflecting material, especially Ag, Al, Au, Cu, Cr, Ge, Mo, Ni,Si, Ti, the alloys thereof, graphite, Fe₂O₃ or MoS₂, particularlypreferably Al or MoS₂. If Al forms the reflective layer and thereflective layer should be retained, temperatures above 600° C. shouldbe avoided to prevent reaction of the Al with silicon and/or siliconoxide contained in the neighbouring layers. If Al forms the reflectivelayer and the flakes are heated to temperatures above 600° C., the Alreacts with silicon and/or silicon oxide contained in the neighbouringlayers and the reflective layer is converted into a transparent aluminumsilicate layer.

If Al is used as metal of layer (b1), the thickness of layer (b1) isgenerally 20 to 100 nm, especially 40 to 60 nm. The Al is evaporated attemperatures of more than 1000° C.

The thickness of layers (a1) and (c1) is generally 2 to 500 nm,especially 50 to 300 nm.

In a further preferred embodiment, the substrate comprises in this order

-   (a2) a SiO_(0.70-0.99) layer,-   (b2) a SiO_(1.00-1.8) layer, and-   (c2) a SiO_(0.70-0.99) layer.

The substrates comprising layers (a2), (b2) and (c2) are prepared by aprocess comprising the steps:

-   a) vapour-deposition of a separating agent onto a movable carrier to    produce a separating agent layer,-   b1) vapour-deposition of a SiO_(y) layer onto the separating agent    layer, wherein 0.70≦y≦0.99,-   b2) vapour-deposition of a SiO_(y) layer, wherein 1.0≦y≦1.8 onto the    layer obtained in step (b1),-   b3) vapour-deposition of a SiO_(y) layer, wherein 0.70≦y≦0.99, onto    the layer obtained in step (b2),-   c) dissolution of the separating agent layer in a solvent, and-   d) separation of the SiO_(0.70-0.99)/SiO_(1.0-1.8)/SiO_(0.70-0.99)    particles from the solvent.

If step (b3) is omitted, unsymmetrical pigments comprising layers (a2)and (b2) are obtained.

The SiO_(1.00-1.8) layer in step b) is formed preferably from siliconmonoxide vapour produced in the vaporiser by reaction of a mixture of Siand SiO₂ at temperatures of more than 1300° C.

The SiO_(0.70-0.99) layer in step b) is formed preferably by evaporatingsilicon monoxide containing silicon in an amount up to 20% by weight attemperatures of more than 1300° C.

In a further preferred embodiment, the substrate comprises in thisorder:

-   (a3) a SiO_(1.00-1.8) layer,-   (b3) a SiO_(0.70-0.99) layer, and-   (c3) a SiO_(1.00-1.8) layer.

The substrates comprising layers (a3), (b3) and (c3) are prepared by aprocess comprising the steps:

-   a) vapour-deposition of a separating agent onto a movable carrier to    produce a separating agent layer,-   b1) vapour-deposition of a SiO_(y) layer onto the separating agent    layer, wherein 1.0≦y≦1.8,-   b2) vapour-deposition of a SiO_(y) layer, wherein 0.70≦y≦0.99, onto    the layer obtained in step (b1),-   b3) vapour-deposition of a SiO_(y) layer, wherein 1.0≦y≦1.8, layer    onto the layer obtained in step (b2).-   c) dissolution of the separating agent layer in a solvent,-   d) separation of the SiO_(1.0-1.8)/SiO_(0.70-0.99)/SiO_(1.0-1.8)    particles from the solvent.

The SiO_(1.00-1.8) layer in step b1) and b3) is formed preferably fromsilicon monoxide vapour produced in the vaporiser by reaction of amixture of Si and SiO₂ at temperatures of more than 1300° C.

The SiO_(0.70-0.99) layer in step b2) is formed preferably byevaporating silicon monoxide containing silicon in an amount up to 20%by weight at temperatures of more than 1300° C.

If, under industrial vacuums of a few 10⁻² Pa, Si is vaporised (insteadof Si/SiO₂ or SiO/Si) silicon oxides can be obtained which have anoxygen content of less than 0.95, that is to say SiO_(x), wherein0.03≦x≦0.95 (WO03/076520).

If step (b3) is omitted, unsymmetrical pigments comprising layers (a3)and (b3) are obtained.

The thickness of layer (b3) is generally 50 to 400 nm, especially 100 to300 nm.

The thickness of layers (a3) and (c3) is generally 50 to 200 nm,especially 50 to 100 nm.

The colour effect of the pigments can generally be adjusted by way of

-   -   the thickness of the TiO₂ layer,    -   the thickness of the intermediate layer and    -   the composition of the intermediate layer.

It is assumed that calcining TiO₂/SiO_(y) in a non-oxidising atmosphereproduces an intermediate layer that causes a change in the refractiveindex. However, the possibility that the intermediate layer is not acontinuous layer and that, rather, only individual regions at theinterface of TiO₂ and SiO_(y) undergo a conversion that causes a changein the refractive index cannot be ruled out it is further assumed thatthe change in the refractive index is due to the reduction of TiO₂ bySiO_(y). The principle according to the invention is based, therefore,on producing, by reduction of TiO₂ with SiO_(y) (or Al), an intermediatelayer that causes a change in the refractive index.TiO₂+SiO_(y)→SiO_(y+b)+TiO_(2-b)

At present, it can not be excluded, that by heating TiO₂/SiO_(y)particles in an oxygen-free atmosphere, i.e. an argon or heliumatmosphere, or in a vacuum of less than 13 Pa (10⁻¹ Torr), at atemperature above 400° C., especially 400 to 1100° C., besides thereduction of TiO₂ by SiO_(y) SiO_(y) disproportionates in SiO₂ and Si(PCT/EP03/50229).SiO_(y)→(y/y+a) SiO_(y+a)+(1−(y/y+a)) Si

In this disproportion SiO_(y+a) flakes are formed, containing(1−(y/y+a)) Si, wherein 0.03≦y≦1.95, especially 0.70≦y≦0.99 or 1≦y≦1.8,0.05≦a≦1.97, especially 0.05≦a≦1.30, and the sum y and a is equal orless than 2. SiO_(y+a) is an oxygen enriched silicon suboxide.

Various coating processes can be utilized in forming additional coatinglayers. Suitable methods for forming the coating layer include vacuumvapor deposition, sol-gel hydrolysis, CVD in a fluidized bed (U.S. Pat.No. 5,364,467 and U.S. Pat. No. 5,763,086), and electrochemicaldeposition. Another depositing method is the plasma enhanced chemicalvapor deposition (PECVD) where the chemical species are activated by aplasma. Such a method is disclosed in detail in WO02/31058.

In principle, the plane parallel pigments can comprise in additionmaterials having a “low” index of refraction, which is defined herein asan index of refraction of about 1.65 or less, and/or can have a “high”index of refraction, which is defined herein as an index of refractionof greater than about 1.65, and/or semi-transparent metal layers.Various (dielectric) materials that can be utilized include inorganicmaterials such as metal oxides, metal fluorides, metal sulfides, metalnitrides, metal carbides, combinations thereof, and the like, as well asorganic dielectric materials. These materials are readily available andeasily applied by physical or chemical vapor deposition processes.

Non limiting examples of suitable low index dielectric materials thatcan be used include silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), andmetal fluorides such as magnesium fluoride (MgF₂), aluminum fluoride(AlF₃), cerium fluoride (CeF₃), lanthanum fluoride (LaF₃), sodiumaluminum fluorides (e.g., Na₃AlF₆ or Na₅Al₃F₁₄), neodymium fluoride(NdF₃), samarium fluoride (SmF₃), barium fluoride (BaF₂), calciumfluoride (CaF₂), lithium fluoride (LiF), combinations thereof, or anyother low index material having an index of refraction of about 1.65 orless. For example, organic monomers and polymers can be utilized as lowindex materials, including dienes or alkenes such as acrylates (e.g.,methacrylate), polymers of perfluoroalkenes, polytetrafluoroethylene(TEFLON), polymers of fluorinated ethylene propylene (FEP), parylene,p-xylene, combinations thereof, and the like. Additionally, theforegoing materials include evaporated, condensed and cross-linkedtransparent acrylate layers, which may be deposited by methods describedin U.S. Pat. No. 5,877,895.

Suitable metals for the semi-transparent metal layer are, for example,Cr, Ti, Mo, W, Al, Cu, Ag, Au, or Ni.

Examples of the dielectric material having a “high” refractive index,that is to say a refractive index greater than about 1.65, preferablygreater than about 2.0, most preferred greater than about 2.2, are zincsulfide (ZnS), zinc oxide (ZnO), zirconium oxide (ZrO₂), titaniumdioxide (TiO₂), carbon, indium oxide (In₂O₃), indium tin oxide (ITO),tantalum pentoxide (Ta₂O₅), chromium oxide (Cr₂O₃), cerium oxide (CeO₂),yttrium oxide (y203), europium oxide (Eu₂O₃), iron oxides such asiron(II)/iron(III) oxide (Fe₃O₄) and iron(III) oxide (Fe₂O₃), hafniumnitride (HfN), hafnium carbide (HfC), hafnium oxide (HfO₂), lanthanumoxide (La₂O₃), magnesium oxide (MgO), neodymium oxide (Nd₂O₃),praseodymium oxide (Pr₆O₁₁), samarium oxide (Sm₂O₃), antimony trioxide(Sb₂O₃), silicon monoxides (SiO), selenium trioxide (Se₂O₃), tin oxide(SnO₂), tungsten trioxide (WO₃) or combinations thereof. The dielectricmaterial is preferably a metal oxide, it being possible for the metaloxide to be a single oxide or a mixture of oxides, with or withoutabsorbing properties, for example TiO₂, ZrO₂, Fe₂O₃, Fe₃O₄, Cr₂O₃ orZnO, with TiO₂ being especially preferred.

The metal oxide layers can be applied by CVD (chemical vapourdeposition) or by wet chemical coating. The metal oxide layers can beobtained by decomposition of metal carbonyls in the presence of watervapour (relatively low molecular weight metal oxides such as magnetite)or in the presence of oxygen and, where appropriate, water vapour (e.g.nickel oxide and cobalt oxide). The metal oxide layers are especiallyapplied by means of oxidative gaseous phase decomposition of metalcarbonyls (e.g. iron pentacarbonyl, chromium hexacarbonyl; EP-A-45851),by means of hydrolytic gaseous phase decomposition of metal alcoholates(e.g. titanium and zirconium tetra-n- and -iso-propanolate;DE-A-4140900) or of metal halides (e.g. titanium tetrachloride;EP-A-338428), by means of oxidative decomposition of organyl tincompounds (especially alkyl tin compounds such as tetrabutyltin andtetramethyltin; DE-A4403678) or by means of the gaseous phase hydrolysisof organyl silicon compounds (especially di-tert-butoxyacetoxysilane)described in EP-A-668329, it being possible for the coating operation tobe carried out in a fluidised-bed reactor (EP-A-045851 and EP-A-106235).Al₂O₃ layers (B) can advantageously be obtained by controlled oxidationduring the cooling of aluminium-coated pigments, which is otherwisecarried out under inert gas (DE-A-19516181).

It is possible to obtain pigments that are more intense in colour andmore transparent by applying, on top of the TiO₂ layer, a metal oxide oflow refractive index, such as SiO₂, Al₂O₃, AlOOH, B₂O₃ or a mixturethereof, preferably SiO₂, and applying a further TiO₂ layer on top ofthe latter layer (EP-A-892832, EP-A-753545, WO93/08237, WO98/53011,WO98/12266, WO98/38254, WO99/20695, WO00/42111 and EP-A-1 213 330).

Where appropriate, an SiO₂ (protective) layer can be applied on top ofthe titanium dioxide layer, for which the following method may be used:A soda water glass solution is metered into a suspension of the materialbeing coated, which suspension has been heated to approximately 50-100°C., especially 70-80° C. The pH is maintained at from 4 to 10,preferably from 6.5 to 8.5, by simultaneously adding 10% hydrochloricacid. After addition of the water glass solution, stirring is carriedout for a further 30 minutes.

It is furthermore possible to subject the finished pigment to subsequentcoating or subsequent treatment which further increases the light,weather and chemical stability or which facilitates handling of thepigment, especially its incorporation into various media. For example,the procedures described in DE-A-2215191, DE-A-3151354, DE-A-3235017,DE-A-3334598, DE-A-4030727, EP-A649886, WO97/29059, WO99/57204, and U.S.Pat. No. 5,759,255 are suitable as subsequent treatment or subsequentcoating.

It is also possible to reduce the TiO₂ present on the surface of thepigments by means of the processes described in DE-A-19502231,WO97/39065, WO00/17277 and especially DE-A-19843014, thereby formingtitanium suboxides, metal oxides, non-metal oxides, titanium nitridesand/or titanium oxynitrides.

The reducing agents employed are gaseous reducing agents, such as, forexample, hydrogen, or solid reducing agents in the form of metalpowders, alloys of metals, metal borides, metal carbides or metalsilicides. The use of powders of metals/non-metals, such as boron,aluminium, silicon, zinc or iron and especially silicon or combinationsthereof is preferred.

Customary reducing agents such as the alkali metals may be used in theliquid or gaseous phase. Other reducing agents to be mentioned arehydrides, such as LiH or CaH₂. Combinations of those reducing agentswith one another are also suitable.

The titanium-dioxide-coated platelets are intensively mixed with theabove-described solid reducing agents in a ratio of from 100:1 to 5:1and treated in a non-oxidising atmosphere at temperatures of more than600° C., preferably in the range from 700 to 1100° C., for more than 10minutes, preferably for from 15 to 60 minutes.

The reduction reaction is accelerated in the presence of a halide,preferably a chloride. Preference is especially given to LiCl, NaCl,KCl, MgCl₂, CaCl₂, CuCl₂, CrCl₃, MnCl₂, FeCl₂, FeCl₃, CoCl₂, NiCl₂ orCeCl₃. The reaction temperature can be reduced by from 150 to 300° C. inthe presence of a chloride, such as, for example, CaCl₂. The chlorideshould preferably be anhydrous. The amounts of halide may be from 0.1 to40% by weight, preferably from 0.5 to 10% by weight, based on the SiO₂platelet coated with TiO₂. In addition, the pigment according to theinvention can also be coated with poorly soluble, firmly adhering,inorganic or organic colourants. Preference is given to the use ofcolour lakes and, especially, aluminium colour lakes. For that purposean aluminium hydroxide layer is precipitated, which is, in a secondstep, laked by using a colour lake (DE-A-2429762 and DE-A-2928287).

Furthermore, the pigment according to the invention may also have anadditional coating with complex salt pigments, especially cyanoferratecomplexes (EP-A-141173 and DE-A-2313332).

The pigment according to the invention may also be coated with organicdyes and especially with phthalocyanine or metal phthalocyanine and/orindanthrene dyes in accordance with DE-A-4009567.

Coloured pigments can be produced by mixing TiO₂-coated SiO_(z)platelets with at least one solid reducing agent, preferably an alkalineearth metal, B, Al, Si, Zn, Fe, LiH, CaH₂, Al₄C₃, Mg₂Si, MgSi₂, Ca₂Si orCaSi₂, and calcining the mixture in a non-oxidising gas atmosphere forlonger than 10 minutes at a temperature above 600° C. The reductionreaction takes place in a non-oxidising gas atmosphere, such as, forexample, N₂, Ar, He, CO₂, H₂ or NH₃, preference being given to N₂ or Ar.Preference is also given to hydrogen/nitrogen mixtures having a hydrogencontent of preferably 3% by volume. In the case of N₂ or NH₃, TiN orTiON may be produced in addition to TiO_(2-x).

The pigments according to the invention are distinguished by a highgloss and a very uniform thickness, as a result of which very highcolour purity and colour strength are obtained. The pigments accordingto the invention can be used for all customary purposes, for example forcolouring textiles, polymers in the mass, coatings (including effectfinishes, including those for the automotive sector), glazes forceramics and glasses, and printing inks (including those for securityprinting), and also, for example, for applications in cosmetics and inink-jet printing. Such applications are known from reference works, forexample “Industrielle Organische Pigmente” (W. Herbst and K. Hunger, VCHVeriagsgesellschaft mbH Weinhelm/New York, 2nd, completely revisededition, 1995).

The pigments according to the invention are effect pigments (metaleffect pigments and interference pigments), that is to say, pigmentsthat, besides imparting colour to an application medium, impartadditional properties such as, for example, angle dependence of thecolour (flop), lustre (not surface gloss) or texture. On metal effectpigments, substantially directed reflection occurs at directionallyoriented pigment particles. In the case of interference pigments, thecolour-imparting effect is due to the phenomenon of interference oflight in thin, highly refractive layers. The pigments according to theinvention may be goniochromatic and brilliant and produce highlysaturated (bright) colours. They are accordingly very especiallysuitable for combination with conventional, transparent pigments, forexample organic pigments such as, for example, diketopyrrolopyrroles,quinacridones, dioxazines, perylenes, isoindolinones etc. Thetransparent pigment may have a similar colour to the effect pigment.Especially interesting combination effects are obtained, however, inanalogy to, for example, EP-A388932 or EP-A402943, when the colour ofthe transparent pigment and that of the effect pigment arecomplementary.

The pigments according to the invention can be used with excellentresults for pigmenting high molecular weight organic material.

The high molecular weight organic material for the pigmenting of whichthe pigments or pigment compositions according to the invention may beused may be of natural or synthetic origin. High molecular weightorganic materials usually have molecular weights of about from 10³ to10⁸ g/mol or even more. They may be, for example, natural resins, dryingoils, rubber or casein, or modified natural substances, such aschlorinated rubber, oil-modified alkyd resins, viscose, cellulose ethersor esters, such as ethylcellulose, cellulose acetate, cellulosepropionate, cellulose acetobutyrate or nitrocellulose, but especiallytotally synthetic organic polymers (thermosetting plastics andthermoplastics), as are obtained by polymerisation, polycondensation orpolyaddition. From the class of the polymerisation resins there may bementioned, especially, polyolefins, such as polyethylene, polypropyleneor polyisobutylene, and also substituted polyolefins, such aspolymerisation products of vinyl chloride, vinyl acetate, styrene,acrylonitrile, acrylic acid esters, methacrylic acid esters orbutadiene, and also copolymerisation products of the said monomers, suchas especially ABS or EVA. From the series of the polyaddition resins andpolycondensation resins there may be mentioned condensation products offormaldehyde with phenols, so-called phenoplasts, and condensationproducts of formaldehyde with urea, thiourea or melamine, so-calledamino-plasts, and the polyesters used as surface-coating resins, eithersaturated, such as alkyd resins, or unsaturated, such as maleate resins;also linear polyesters and polyamides, poly-urethanes or silicones.

The said high molecular weight compounds may be present singly or inmixtures, in the form of plastic masses or melts. They may also bepresent in the form of their monomers or in the polymerised state indissolved form as film-formers or binders for coatings or printing inks,such as, for example, boiled linseed oil, nitrocellulose, alkyd resins,melamine resins and urea-formaldehyde resins or acrylic resins.

Depending on the intended purpose, it proves advantageous to use theeffect pigments or effect pigment compositions according to theinvention as toners or in the form of preparations. Depending on theconditioning method or intended application, it may be advantageous toadd certain amounts of texture-improving agents to the effect pigmentbefore or after the conditioning process, provided that this has noadverse effect on use of the effect pigments for colouring highmolecular weight organic materials, especially polyethylene. Suitableagents are, especially, fatty acids containing at least 18 carbon atoms,for example stearic or behenic acid, or amides or metal salts thereof,especially magnesium salts, and also plasticisers, waxes, resin acids,such as abietic acid, rosin soap, alkylphenols or aliphatic alcohols,such as stearyl alcohol, or aliphatic 1,2-dihydroxy compounds containingfrom 8 to 22 carbon atoms, such as 1,2-dodecanediol, and also modifiedcolophonium maleate resins or fumaric acid colophonium resins. Thetexture-improving agents are added in amounts of preferably from 0.1 to30% by weight, especially from 2 to 15% by weight, based on the endproduct.

The effect pigments according to the invention can be added in anytinctorially effective amount to the high molecular weight organicmaterial being pigmented. A pigmented composition comprising a highmolecular weight organic material and from 0.01 to 80% by weight,preferably from 0.1 to 30% by weight, based on the high molecular weightorganic material, of an effect pigment according to the invention isadvantageous. Concentrations of from 1 to 20% by weight, especially ofabout 10% by weight, can often be used in practice.

High concentrations, for example those above 30% by weight, are usuallyin the form of concentrates (“masterbatches”) which can be used ascolorants for producing pigmented materials having a relatively lowpigment content, the pigments according to the invention having anextraordinarily low viscosity in customary formulations with the resultthat the latter can still be processed well.

For the purpose of pigmenting organic materials, the effect pigmentsaccording to the invention may be used singly. It is, however, alsopossible, in order to achieve different hues or colour effects, to addany desired amounts of other colour-imparting constituents, such aswhite, coloured, black or effect pigments, to the high molecular weightorganic substances in addition to the effect pigments according to theinvention. When coloured pigments are used in admixture with the effectpigments according to the invention, the total amount is preferably from0.1 to 10% by weight, based on the high molecular weight organicmaterial. The preferred combination of an effect pigment according tothe invention with a coloured pigment of another colour, especially of acomplementary colour, has especially high goniochromicity, colorationsmade using the effect pigment and colorations made using the colouredpigment having, at a measurement angle of 10°, a difference in hue (ΔH*)of from 20 to 340, especially from 150 to 210.

Preferably, the effect pigments according to the invention are combinedwith transparent coloured pigments, it being possible for thetransparent coloured pigments to be present either in the same medium asthe effect pigments according to the invention or in a neighbouringmedium. An example of an arrangement in which the effect pigment and thecoloured pigment are advantageously present in neighbouring media is amulti-layer effect finish.

The pigmenting of high molecular weight organic substances with thepigments according to the invention is carried out, for example, byadmixing such a pigment, where appropriate in the form of a masterbatch,with the substrates using roll mills or mixing or grinding apparatuses.The pigmented material is then brought into the desired final form usingmethods known per se, such as calendering, compression moulding,extrusion, coating, pouring or injection moulding. Any additivescustomary in the plastics industry, such as plasticisers, fillers orstabilisers, can be added to the polymers, in customary amounts, beforeor after incorporation of the pigment in particular, in order to producenon-rigid shaped articles or to reduce their brittleness, it isdesirable to add plasticisers, for example esters of phosphoric add,phthalic acid or sebacic acid, to the high molecular weight compoundsprior to shaping. For pigmenting coatings and printing inks, the highmolecular weight organic materials and the effect pigments according tothe invention, where appropriate together with customary additives suchas, for example, fillers, other pigments, siccatives or plasticisers,are finely dispersed or dissolved in the same organic solvent or solventmixture, it being possible for the individual components to be dispersedor dissolved separately or for a number of components to be dispersed ordissolved together, and only thereafter for all the components to bebrought together.

During dispersion of an effect pigment according to the invention in thehigh molecular weight organic material being pigmented and duringprocessing of a pigment composition according to the invention,conditions under which only relatively weak shearing forces occur arepreferably maintained so that the effect pigment will not be broken upinto smaller fragments. Plastics comprising the pigment of the inventionin amounts of 0.1 to 50% by weight, in particular 0.5 to 7% by weight inthe coating sector, the pigments of the invention are employed inamounts of 0.1 to 10% by weight in the pigmentation of binder systems,for example for paints and printing inks for intaglio, offset or screenprinting, the pigment is incorporated into the printing ink in amountsof 0.1 to 50% by weight, preferably 5 to 30% by weight and in particular8 to 15% by weight The colorations obtained, for example in plastics,coatings or printing inks, especially in coatings or printing inks, moreespecially in coatings, are distinguished by excellent properties,especially by extremely high saturation, outstanding fastness propertiesand high goniochromicity. When the high molecular weight material beingpigmented is a coating, it is especially a speciality coating, mostespecially an automotive finish.

The pigments according to the invention are also suitable for making-upthe lips or the skin and for colouring the hair or the nails.

The invention accordingly relates also to a cosmetic preparation orformulation comprising from 0.0001 to 90% by weight of thesilicon/silicon oxide flakes and/or of a pigment according to theinvention and from 10 to 99.9999% of a cosmetically suitable carriermaterial, based on the total weight of the cosmetic preparation orformulation.

Such cosmetic preparations or formulations are, for example, lipsticks,blushers, foundations, nail varnishes and hair shampoos.

The pigments may be used singly or in the form of mixtures. It is, inaddition, possible to use pigments according to the invention togetherwith other pigments and/or colorants, for example in combinations asdescribed hereinbefore or as known in cosmetic preparations. Thecosmetic preparations and formulations according to the inventionpreferably contain the pigment according to the invention in an amountfrom 0.005 to 50% by weight, based on the total weight of thepreparation.

Suitable carrier materials for the cosmetic preparations andformulations according to the invention include the customary materialsused in such compositions.

The cosmetic preparations and formulations according to the inventionmay be in the form of, for example, sticks, ointments, creams,emulsions, suspensions, dispersions, powders or solutions. They are, forexample, lipsticks, mascara preparations, blushers, eye-shadows,foundations, eyeliners, powder or nail varnishes.

If the preparations are in the form of sticks, for example lipsticks,eye-shadows, blushers or foundations, the preparations consist for aconsiderable part of fatty components, which may consist of one or morewaxes, for example ozokerite, lanolin, lanolin alcohol, hydrogenatedlanolin, acetylated lanolin, lanolin wax, beeswax, candelilla wax,microcrystalline wax, carnauba wax, cetyl alcohol, stearyl alcohol,cocoa butter, lanolin fatty acids, petrolatum, petroleum jelly, mono-,di- or tri-glycerides or fatty esters thereof that are solid at 25° C.,silicone waxes, such as methyloctadecane-oxypolysiloxane andpoly(dimethylsiloxy)-stearoxysiloxane, stearic acid monoethanolamine,colophane and derivatives thereof, such as glycol abietates and glycerolabietates, hydrogenated oils that are solid at 25° C., sugar glyceridesand oleates, myristates, lanolates, stearates and dihydroxystearates ofcalcium, magnesium, zirconium and aluminium.

The fatty component may also consist of a mixture of at least one waxand at least one oil, in which case the following oils, for example, aresuitable: paraffin oil, purcelline oil, perhydrosqualene, sweet almondoil, avocado oil, calophyllum oil, castor oil, sesame oil, jojoba oil,mineral oils having a boiling point of about from 310 to 410° C.,silicone oils, such as dimethylpolysiloxane, linoleyl alcohol, linolenylalcohol, oleyl alcohol, cereal grain oils, such as wheatgerm oil,isopropyl lanolate, isopropyl palmitate, isopropyl myristate, butylmyristate, cetyl myristate, hexadecyl stearate, butyl stearate, decyloleate, acetyl glycerides, octanoates and decanoates of alcohols andpolyalcohols, for example of glycol and glycerol, ricinoleates ofalcohols and polyalcohols, for example of cetyl alcohol, isostearylalcohol, isocetyl lanolate, isopropyl adipate, hexyl laurate and octyldodecanol.

The fatty components in such preparations in the form of sticks maygenerally constitute up to 99.91% by weight of the total weight of thepreparation.

The cosmetic preparations and formulations according to the inventionmay additionally comprise further constituents, such as, for example,glycols, polyethylene glycols, polypropylene glycols, monoalkanolamides,non-coloured polymeric, inorganic or organic fillers, preservatives, UVfilters or other adjuvants and additives customary in cosmetics, forexample a natural or synthetic or partially synthetic di- ortri-glyceride, a mineral oil, a silicone oil, a wax, a fatty alcohol, aGuerbet alcohol or ester thereof, a lipophilic functional cosmeticactive ingredient, including sun-protection filters, or a mixture ofsuch substances.

A lipophilic functional cosmetic active ingredient suitable for skincosmetics, an active ingredient composition or an active ingredientextract is an ingredient or a mixture of ingredients that is approvedfor dermal or topical application. The following may be mentioned by wayof example:

-   -   active ingredients having a cleansing action on the skin surface        and the hair; these include all substances that serve to cleanse        the skin, such as oils, soaps, synthetic detergents and solid        substances;    -   active ingredients having a deodorising and        perspiration-inhibiting action: they include antiperspirants        based on aluminium salts or zinc salts, deodorants comprising        bactericidal or bacteriostatic deodorising substances, for        example triclosan, hexachlorophene, alcohols and cationic        substances, such as, for example, quaternary ammonium salts, and        odour absorbers, for example ®Grillocin (combination of zinc        ricinoleate and various additives) or triethyl citrate        (optionally in combination with an antioxidant, such as, for        example, butyl hydroxytoluene) or ion-exchange resins;    -   active ingredients that offer protection against sunlight (UV        filters): suitable active ingredients are filter substances        (sunscreens) that are able to absorb UV radiation from sunlight        and convert it into heat: depending on the desired action, the        following light-protection agents are preferred:        light-protection agents that selectively absorb sunburn-causing        high-energy UV radiation in the range of approximately from 280        to 315 nm (UV-B absorbers) and transmit the longer-wavelength        range of, for example, from 315 to 400 nm (UV-A range), as well        as light-protection agents that absorb only the        longer-wavelength radiation of the UV-A range of from 315 to 400        nm (UV-A absorbers); suitable light-protection agents are, for        example, organic UV absorbers from the class of the        p-aminobenzoic acid derivatives, salicylic acid derivatives,        benzophenone derivatives, dibenzoylmethane derivatives, diphenyl        acrylate derivatives, benzofuran derivatives, polymeric UV        absorbers comprising one or more organosilicon radicals,        cinnamic acid derivatives, camphor derivatives,        trianilino-s-triazine derivatives, phenyl-benzimidazolesulfonic        acid and salts thereof, menthyl anthranilates, benzotriazole        derivatives, and/or an inorganic micropigment selected from        aluminium oxide- or silicon dioxide-coated TiO₂, zinc oxide or        mica;    -   active ingredients against insects (repellents) are agents that        are intended to prevent insects from touching the skin and        becoming active there; they drive insects away and evaporate        slowly; the most frequently used repellent is diethyl toluamide        (DEET); other common repellents will be found, for example, in        “Pflegekosmetik” (W. Raab and U. Kindl, Gustav-Fischer-Verlag        Stuttgart/New York, 1991) on page 161;    -   active ingredients for protection against chemical and        mechanical influences: these include all substances that form a        barrier between the skin and external harmful substances, such        as, for example, paraffin oils, silicone oils, vegetable oils,        PCL products and lanolin for protection against aqueous        solutions, film-forming agents, such as sodium alginate,        triethanolamine alginate, polyacrylates, polyvinyl alcohol or        cellulose ethers for protection against the effect of organic        solvents, or substances based on mineral oils, vegetable oils or        silicone oils as “lubricants” for protection against severe        mechanical stresses on the skin;    -   moisturising substances: the following substances, for example,        are used as moisture-controlling agents (moisturisers): sodium        lactate, urea, alcohols, sorbitol, glycerol, propylene glycol,        collagen, elastin and hyaluronic acid;    -   active ingredients having a keratoplastic effect benzoyl        peroxide, retinoic acid, colloidal sulfur and resorcinol;    -   antimicrobial agents, such as, for example, triclosan or        quaternary ammonium compounds;    -   oily or oil-soluble vitamins or vitamin derivatives that can be        applied dermally: for example vitamin A (retinol in the form of        the free acid or derivatives thereof), panthenol, pantothenic        acid, folic acid, and combinations thereof, vitamin E        (tocopherol), vitamin F; essential fatty acids; or niacinamide        (nicotinic acid amide);    -   vitamin-based placenta extracts: active ingredient compositions        comprising especially vitamins A, C, E, B₁, B₂, B₆, B₁₂, folic        acid and blotin, amino acids and enzymes as well as compounds of        the trace elements magnesium, silicon, phosphorus, calcium,        manganese, iron or copper,    -   skin repair complexes: obtainable from inactivated and        disintegrated cultures of bacteria of the bifidus group;    -   plants and plant extracts: for example arnica, aloe, beard        lichen, ivy, stinging nettle, ginseng, henna, camomile,        marigold, rosemary, sage, horsetail or thyme;    -   animal extracts: for example royal jelly, propolis, proteins or        thymus extracts;    -   cosmetic oils that can be applied dermally: neutral oils of the        Miglyol 812 type, apricot kernel oil, avocado oil, babassu oil,        cottonseed oil, borage oil, thistle oil, groundnut oil,        gamma-oryzanol, rosehip-seed oil, hemp oil, hazelnut oil,        blackcurrant-seed oil, jojoba oil, cherry-stone oil, salmon oil,        linseed oil, cornseed oil, macadamia nut oil, almond oil,        evening primrose oil, mink oil, olive oil, pecan nut oil, peach        kernel oil, pistachio nut oil, rape oil, rice-seed oil, castor        oil, safflower oil, sesame oil, soybean oil, sunflower oil, tea        tree oil, grapeseed oil or wheatgerm oil.

The preparations in stick form are preferably anhydrous but may incertain cases comprise a certain amount of water which, however, ingeneral does not exceed 40% by weight, based on the total weight of thecosmetic preparation.

If the cosmetic preparations and formulations according to the inventionare in the form of semi-solid products, that is to say in the form ofointments or creams, they may likewise be anhydrous or aqueous. Suchpreparations and formulations are, for example, mascaras, eyeliners,foundations, blushers, eye-shadows, or compositions for treating ringsunder the eyes.

If, on the other hand, such ointments or creams are aqueous, they areespecially emulsions of the water-in-oil type or of the oil-in-watertype that comprise, apart from the pigment, from 1 to 98.8% by weight ofthe fatty phase, from 1 to 98.8% by weight of the aqueous phase and from0.2 to 30% by weight of an emulsifier.

Such ointments and creams may also comprise further conventionaladditives, such as, for example, perfumes, antioxidants, preservatives,gel-forming agents, UV filters, colorants, pigments, pearlescent agents,non-coloured polymers as well as inorganic or organic fillers. If thepreparations are in the form of a powder, they consist substantially ofa mineral or inorganic or organic filler such as, for example, talcum,kaolin, starch, polyethylene powder or polyamide powder, as well asadjuvants such as binders, colorants etc.

Such preparations may likewise comprise various adjuvants conventionallyemployed in cosmetics, such as fragrances, antioxidants, preservativesetc.

If the cosmetic preparations and formulations according to the inventionare nail varnishes, they consist essentially of nitrocellulose and anatural or synthetic polymer in the form of a solution in a solventsystem, it being possible for the solution to comprise other adjuvants,for example pearlescent agents.

In that embodiment, the coloured polymer is present in an amount ofapproximately from 0.1 to 5% by weight

The cosmetic preparations and formulations according to the inventionmay also be used for colouring the hair, in which case they are used inthe form of shampoos, creams or gels that are composed of the basesubstances conventionally employed in the cosmetics industry and apigment according to the invention.

The cosmetic preparations and formulations according to the inventionare prepared in conventional manner, for example by mixing or stirringthe components together, optionally with heating so that the mixturesmelt.

The Examples that follow illustrate the invention without limiting thescope thereof. Unless otherwise indicated, percentages and parts arepercentages and parts by weight, respectively.

EXAMPLES Example 1

Under a high vacuum, a layer of TiO₂ (100 nm), a layer of SiO (100 nm)and a layer of TiO₂ (100 nm) are sublimated in that order onto a glassplate. One sample is used as a reference sample (Sample 1) and the othersample (Sample 2) is heated in a nitrogen atmosphere for 2 hours at 550°C.

The reflection spectra at 10 degrees and 65 degrees of Samples 1 and 2are shown in FIG. 1. It will be apparent from FIG. 1 that calciningcauses a change in the reflection maximum, but not in the reflectionminimum, which points to a change in the refractive index at theTiO₂/SiO interface, which is presumably due to the reduction of TiO₂ bySiO.

The L*, a*, b*, c* and h values (CIELAB system) of Samples 1 and 2 areset out in the following Table:

Viewing angle Sample Calcining [degrees] L* a* b* c* h 1 no 10 44.2 10.39.9 14.3 44.1 2 yes 10 45.5 16 14.6 21.7 42.3 1 no 65 65.7 11.6 15.419.3 52.9 2 yes 65 67.3 12 19.8 23.1 58.8

Example 2

SiO_(y) flakes are made by sublimation of SiO under a vacuum of lessthan 0.1 Pa. The substrate is previously coated with 100 nm of a releaselayer of NaCl. The substrate is washed with deionised water, theobtained flakes are washed with deionised water in order to remove theNaCl and dried. White looking SiO_(y) flakes having a thickness of 245nm +/−5% are obtained. The SiO_(y) flakes look blue under a microscopeworking with reflecting light. The amplitude of the maximum reflectivityin air is below 10%.

190 mg of the SiO_(y) flakes are added to 44 ml deionised water andstirred in an ultrasonic bath during 10 minutes. The pH of thesuspension is adjusted to 1.4 with 65% nitric acid. The suspension isthen heated up to 75° C. and vigorously stirred while adding a total of1 ml of TiOCl₂ during 60 minutes. The pH is kept constant at 1.4 bycontinuous addition of NaOH. The suspension is further stirred for 2hours at 75° C. and then cooled and filtered. The obtained flakes aredried at 50° C. The TiO₂-coated SiO_(y) flakes look yellow-green underthe microscope working in back light mode. The same TiO₂-coated SiO_(y)flakes look white-greenish in a transparent bottle. The powder is thenheated at 700° C. for 2 hours in a vacuum of less than 10 Pa. Afterheating the TiO₂-coated SiO_(y) flakes look bright green in atransparent bottle. Particles of the TiO₂-coated SiO_(y) flakes lookbright yellow-green with a maximum reflectivity above 20% under amicroscope (working with reflecting light).

1. A platelet-shaped pigment comprising a layer obtained by calciningTiO2 coated SiOy platelet in a non-oxidizing atmosphere, wherein0.03≦y≦1.95, or a platelet-shaped pigment obtained by calcining a TiO2coated Ti, Zr, Cr, or Zn platelet in a non-oxidizing atmosphere at atemperature of more than 600° C.
 2. A pigment according to claim 1,comprising (a) a substrate layer of SiOz, wherein 0.03≦z≦2.0, (b) anintermediate layer obtained by calcining TiO2 coated SiOy platelet,wherein 0.03≦y≦1.95, in a non-oxidizing atmosphere, and (c) a TiO2layer.
 3. A pigment according to claim 1, comprising (a) a multi-layeredplatelet-shaped substrate layer, wherein the substrate layer has a coreof SiO_(x1) which core has a layer of SiO_(x2) SiO_(y1) on the lower andupper surfaces, but not on the side faces, or the substrate layer has acore of SiO_(x2) which core has a layer of SiO_(x1) or SiO_(y1) on thelower and upper surfaces, but not on the side faces, or the substratelayer has a core of SiO_(y1) which core has a layer of SiO_(x1) orSiO_(x2) on the lower and upper surfaces, but not on the side faces, orthe substrate layer has a core of a metal, which core has a layer ofSiO_(x1), SiO_(x2) or a SiO_(y1) on the lower and upper surfaces, butnot on the side faces, (b) an intermediate layer obtained by calciningTiO₂/SiO_(x1), TiO₂/SiO_(x2), or TiO₂/SiO_(y1) in a non-oxidizingatmosphere and (c) a TiO₂ layer, wherein 0.03≦x1<0.70, 0.70≦x2≦0.99, and1.00≦y1≦1.95.
 4. A pigment according to claim 2, wherein the substratelayer has a thickness of from 20 to 1000 nm.
 5. A pigment according toclaim 2, wherein the intermediate layer has a thickness of from 1 to 500nm.
 6. A pigment according to claim 2, wherein the TiO₂ layer has athickness of from 1 to 200 nm.
 7. A process for the production of apigment, wherein (a) TiO₂-coated SiO_(y) platelets, wherein 0.03≦y≦1.95,or TiO₂-coated Ti, Zr, Cr, or Zn platelets, are calcined in anon-oxidising gas atmosphere at a temperature of more than 600° C.
 8. Acosmetic preparation, colorant, coating, printing ink, ink for securityprinting, plastic, textile, or glaze for ceramics and glass, comprisinga pigment according to claim
 1. 9. A platelet-shaped pigment accordingto claim 1, wherein 0.70≦y≦1.8.
 10. A pigment according to claim 2,wherein 0.10≦z≦20.
 11. A pigment according to claim 2, wherein0.70≦z≦20.
 12. A pigment according to claim 3, wherein the metal in themulti-layered platelet-shaped substrate layer having a core of a metalis Al.
 13. A pigment according to claim 3, wherein 0.05≦x1≦0.50,0.70≦x2≦0.99, and 1.1≦y1≦1.8.
 14. A pigment according to claim 2,wherein the intermediate layer has a thickness of from 10 to 50 nm. 15.A pigment according to claim 2, wherein the TiO₂ layer has a thicknessof from 10 to 100 nm.
 16. A pigment according to claim 2, wherein theTiO₂ layer has a thickness of from 20 to 50 nm.
 17. A process accordingto claim 7, wherein 0.70≦y≦1.8.
 18. A process according to claim 7,wherein (a) TiO₂-coated SiO_(y) platelets, wherein 0.03≦y≦1.95, arecalcined in a non-oxidising gas atmosphere at a temperature of more than600° C. and then (b) the TiO₂-coated SiO_(y) platelets are treated at atemperature of more than 200° C., with air or another oxygen-containinggas.
 19. A pigment prepared according to the process of claim
 18. 20. Aprocess according to claim 18, wherein in step (b) the TiO₂-coatedSiO_(y) platelets are treated at a temperature of more than 400° C.,with air or another oxygen-containing gas.